You look at the fragments and then you pick areas where they overlap, given enough copies you should be able to build a contiguous consensus based on overlaps. Theoretically you could have a bunch of frags as short as 4bps long and still be able to get a decent length of sequence.

Living one day at a time; Enjoying one moment at a time; Accepting hardships as the pathway to peace; ~Niebuhr

I second mith until the last sentence. If your sequences are too short, it will be nearimpossible to get a consensus because they won't differ enough to provide enough significant overlap. Sequences the size of a PCR primer (for the exact same reason) would probably be the minimum to assemble something.

Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)